Changelog

Reverse-chronological list of substantive reader-facing changes since project inception. Skips typos, merge commits, and internal-only cleanup unless it changes what readers see.

This changelog is curated from the gen/src/ git history plus recent reader-facing additions. Entries are grouped by what a reader actually experiences.

August 2026 — Wave 9: Problem-page reference-bar quality

2026-08-27 — Wave 9: 205/205 problem pages elevated to STAR quality

All 205 problem pages now score ≥9/10 on a 10-flag rubric (LC link, ≥2 examples, hints widget, ≥2 numbered approaches, drama numbers, interview commentary, complexity table, when-to-use, related problems, ≥5 widgets).

Every enriched page now has:

• Two or three worked examples covering edge cases (empty, single, adversarial).
• Drama numbers in the constraint line — the naive approach's TLE spelled out at concrete scale versus the canonical improvement.
• A numbered ## Approach 1 — Brute … with full working code, complexity, and an explicit "then what's better" transition.
• Italicised "Say aloud in an interview: …" commentary on the canonical approach that maps it back to the algorithmic family.
• A complexity ladder table marking the canonical solution in bold.

Rolled out in six parts (2ef479e, d75a798, 8d1c983, 665ba2a, f3744f7, 155d2a6), enriching 69 pages that had scored 7 or 8. Every family (arrays → quickselect) is now 100 % STAR.

August 2026 — Waves 1–8: Pattern-chapter reference-bar quality

2026-08-26 — Wave 8: Flagship canonical walkthroughs

• Union Find, Topological Sort, Greedy, and Divide & Conquer each got a full brute → intermediate → optimised flagship problem embedded in the chapter (79afd41).

2026-08-26 — Wave 7: Visual & accessibility polish

• All 35 SVGs pass a fresh WCAG-AA audit; all 21 animations covered by global reduced-motion CSS; Playwright a11y suite added and green (e7004fa).

2026-08-26 — Wave 6: Historical grounding

• Ten remaining chapters got a hand-written ## History paragraph (Bellman 1952 for DP, Floyd 1967 for tortoise & hare, Bentley's JDK binary-search bug, etc.). Coverage now 21/21 (629b040).

2026-08-26 — Wave 5: Callout enrichment

• Every chapter carries ≥ 8 highlighted insights (3 keys + 3 traps + 2 invariants) with explicit interview-day triggers (a70ca5c).

2026-08-26 — Wave 4: Story-first opening rewrites

• Ten chapters rewritten to open with a "you-scene" + naive attempt + tension teaser instead of a definition (c39f372).

2026-08-26 — Wave 3: Interactive Vue components

• Six new user-driven anim components shipped: PrefixSumAnim, HashingAnim, MergeIntervalsAnim, TopoSortAnim, GreedyAnim, BitManipAnim. All theme-token-driven, screen-reader friendly, respect prefers-reduced-motion (9a0f1cd).

2026-08-26 — Wave 1 & 2: Narrative bones + anemic-chapter enrichment

• Ten chapters got the missing four sections (Why exists / When / When not / Templates / Traps). Four anemic chapters (Binary Search, BS on Answer, Bit Manip, Quickselect) grew from ~2.5k to ~4.5k words each (2db68c6).

November 2026 — CEO plan execution

2026-11 — Round 20: Behavioral Interview Crash Course

• New Behavioral Crash Course appendix chapter (STAR + 6 archetypes + 15 canonical questions).
• Appendix sidebar now surfaces Interview Day Kit and Behavioral Crash Course explicitly.

2026-11 — Round 19: Personalized Study Plan Generator

• Landing has a Study Plan Generator: pick 1/2/4/8/12 weeks and target level (mid/senior/staff) → get a curated week-by-week plan referencing book chapters.

2026-11 — Round 18: Interactive Roadmap checklist

• Roadmap chapter now has clickable weekly checkboxes with a live progress bar (locally persisted).

2026-11 — Round 17: Bookmarks

• Bookmark button on every problem page (amber pill next to Mark Solved).
• Landing shows your top 10 bookmarks, sorted newest-first.

2026-11 — Round 16: Interview Timer

• Interview Timer collapsible panel on all 205 problem pages — start/pause/reset and save your best time per problem.
• Target-time hints for Medium (20-25 min) and Hard (30-40 min).

2026-11 — Round 15: Streak notification bell + print button

• Bottom-left notification bell nudges you to solve today when your streak is at risk (per-day dismiss).
• Every pattern chapter has a "Print chapter" button for offline reference.

2026-11 — Round 14: Custom 404 + Problem Stats

• Dedicated 404 page with 6 suggested links (patterns / roadmap / all problems / Meta track / traps / day kit) instead of the default VitePress 404.
• Problem index shows your solved / total / percentage with a live progress bar.

2026-11 — Round 13: Reading progress + Back to top

• Fixed gradient progress bar at the top of every page tracking scroll position.
• Floating back-to-top button appears after 400px of scroll.

2026-11 — Round 12: Related Problems widget

• Each problem page now recommends 3 sibling problems from the same pattern for lateral browsing.

2026-11 — Round 11: Spaced repetition (Due For Review)

• Landing surfaces up to 5 problems you last solved 7+ days ago — a targeted spaced-repetition list.
• Mark Solved now stores solve timestamps (backward-compatible with older 'true' values).

2026-11 — Round 10: Related Patterns + RSS refresh

• Every pattern chapter now recommends 3 conceptually related patterns.
• RSS feed refreshed with entries for all recent releases.

2026-11 — Round 9: Interview Day Kit + print-friendly styles

• New Interview Day Kit page — 24-hour countdown checklist with emergency mode.
• Landing gained two new feature cards: Company Tracks (Meta / Google / Amazon) and Interview Day Kit.
• Print CSS added: interactive overlays hidden, hints and code traces stay visible when printing.

2026-11 — Round 8: Company Tracks

• New Meta / Google / Amazon track pages with 4-week problem sequences and level-by-level focus.
• Company Tracks dropdown added to the top navigation.

2026-11 — Round 7: Streaks + Share buttons

• Added a StreakTracker on the landing showing consecutive-day activity with fire-emoji tiers.
• Added ShareButtons using the Web Share API plus Twitter and LinkedIn quick-share.

2026-11 — Round 6: Social proof + support

• Landing gained a Social Proof panel with 4 anonymized composite testimonials.
• Added a Support panel with GitHub Sponsors and Buy Me a Coffee links (monetization Path 1 = free + newsletter/sponsors).

2026-11 — Round 5: Mark solved + storage manager

• Every problem page now has a Mark Solved button (with confetti) that syncs with the pattern progress bar.
• Roadmap now has a Storage Manager to export/import/clear all local progress as JSON.

2026-11 — Round 4: Onboarding tour + page analytics

• First-time visitors see a 6-step onboarding tour highlighting hints, runner, and AI companion.
• Privacy-first client-side page-view counter (no external tracking).

2026-11 — Round 3: Feedback + keyboard shortcuts

• Thumbs up/down + free-text feedback widget on all 205 problem pages.
• Floating keyboard-shortcut hint panel (H = hints, R = runner, A = AI companion).

2026-11 — Round 2: Per-pattern progress bar

• Each of the 21 pattern chapters now shows a live progress bar combining solved problems and quiz scores.
• Landing feature grid refreshed to lead with AI Companion, Hints, and Quizzes.

2026-11 — Round 1: Landing polish + user profile

• Added a "Try it before you read it" strip on the landing.
• User Profile card with solved count now displayed prominently.
• Newsletter capture and AI chat now have dismiss + 30-day expiry.

2026-11 — Wave C: AI companion + pattern videos

• Added an AI Companion chat panel to all 205 problem pages (pattern-templated MVP responses; wired to swap in a real LLM).
• Added a Pattern Video placeholder to all 21 pattern chapters (YouTube/Loom-ready with a "coming soon" fallback).

2026-11 — Wave B: User accounts + email capture

• Local User Profile with solved-count badge (localStorage-only; ready for future cross-device auth).
• Email capture on the landing with local dismiss/success states (backend integration pending user signup).

2026-11 — Wave A: Hints, company tags, quizzes, Java runner

• Progressive 3-hint reveal system on all 205 problem pages.
• Company tags (Meta / Google / Amazon and 60+ others) on 194 problem pages.
• Every one of the 21 pattern chapters now ends with a 5-question quiz (105 questions total).
• Interactive Java runner (CheerpJ WASM in-browser) embedded on all 205 problem pages — no server needed.

August 2026

2026-08-21 — Wave B1+B3 reader navigation additions

• New "How this book compares" page versus Grokking, NeetCode, TakeUForward, and LeetCode Premium.
• New public changelog page so readers can see substantive project changes without reading git history.
• Landing page now links directly to the comparison page.
• Foundations sidebar now exposes the comparison page near the Java foundations chapters.
• Appendix sidebar now exposes the changelog.

2026-08-21 — Content consolidation and Grokking-style expansion

• Consolidated the repository to the latest gen/src/ content source.
• Expanded all 21 pattern chapters with a more consistent mentor-style rhythm.
• Strengthened pattern chapters with recognition cues, when-not-to-use guidance, canonical problems, traps, and interview framing.
• Large chapter updates landed across Sliding Window, Two Pointers, Dynamic Programming, Backtracking, Graphs, Trees, Arrays, Strings, and the remaining pattern/data-structure chapters.
• Preserved the Java-native focus while making the problem explanations more self-contained.

2026-08-21 — Initial public site, PDF pipeline, and appendix set

• Initial VitePress site and GitHub Actions deployment pipeline added.
• PDF pipeline added for the offline reference format.
• 21 core pattern chapters introduced, from Sliding Window through Quickselect, plus bonus Math and Design chapters.
• Java Data Structures Primer, Java DSA Gotchas, Complexity Model, Debugging DSA Code, and Zero-to-Hero Roadmap added as foundations.
• Data-structure deep dives added for arrays, strings, linked lists, stacks/queues, trees, heaps, tries, graphs, and segment/Fenwick trees.
• Appendix chapters added: cheat sheets, self-check drills, master problem index, practice solutions, mock interview transcripts, and traps catalog.
• Java 17 is the default implementation language throughout the reference.

Earlier 2026 — Baseline reference scope

• Core idea established: pattern-first DSA prep for senior/staff interviews.
• Java-native explanations and templates chosen over language-agnostic pseudocode.
• Problem chapters organized around brute force → optimized reasoning → trace → complexity → traps.
• Callout vocabulary introduced for key ideas, invariants, traps, pattern connections, notes, and definitions.